The present disclosure relates to a fuel cell device, an automobile with such a fuel cell device and a method for operating a fuel cell device. In particular, the automobile is driven by liquefied gas (abbreviated as LG), in particular liquefied natural gas (abbreviated as LNG) or liquefied synthetic gas.
Liquefied natural gas is a natural gas that has been converted to liquid form for ease of storage or transport. It takes up about 1/600th the volume of natural gas in the gaseous state. The natural gas is typically condensed into a liquid at close to atmospheric pressure by cooling it to approximately −162° C. (−260° F.), wherein a maximum transport pressure is set at around 25 kPa (4 psi).
Liquefied natural gas achieves a higher reduction in volume than compressed natural gas (abbreviated as CNG) so that the (volumetric) energy density of LNG is 2.4 times greater than that of CNG or 60 percent that of diesel fuel. This makes LNG cost efficient to transport over long distances where pipelines do not exist.
Besides the above mentioned properties of liquefied gas, specially designed cryogenic sea vessels (LNG carriers) or cryogenic road tankers are used for its transport. LNG is principally used for transporting natural gas to markets, where it is regasified and distributed as pipeline natural gas, which can be used in natural gas vehicles.
Its relatively high cost of production and the need to store it in expensive cryogenic tanks have hindered widespread commercial use. On energy basis, LNG production is expected to increase in the near future.
Further, natural gas and synthetic gas (i.e. from biomass or Fischer-Tropsch-Synthesis) are available in huge amount. The transportation of these gases requires typically a liquefication (volumetric benefit as described above).
State of the art applications for gas usage for transportation mostly use compressed natural gas. Therefore, the liquefied gas must be transformed back from liquid to gas phase. Furthermore, to realize an acceptable operating range by reasonable tank size, the gas has to be pressurized. This process is extremely inefficient and energy consuming.
To overcome this bottleneck, such as energy waste, the liquefied gas is directly fueled in the gas tank. It is clear and mandatory that the gas tank for storage of the liquefied gas is typically extremely isolated to minimize the evaporation of the liquefied gas.
The evaporation process and related problems are explained in detail above (1 liter of liquefied gas corresponds to 600 liter natural gas as well as storage conditions of the liquefied gas). In general, evaporation of the liquefied gas is not a challenge during the driving mode of the automobile because the evaporated liquefied gas is burned in a combustion engine, for example, gas turbine or a piston engine. The challenge starts when the automobile is parked at a place with minor or no ventilation and the liquefied gas cannot be stored in special tanks according to the pressure limits of the tanks, such as, for example for Europe, “Pressure Equipment Directive 97/23/EC (PED)” (also see above). This could be, for example, a public or private parking place. During parking mode it is typically not advisable to operate the combustion engine to burn the evaporated gas. It is also dangerous to blow off the evaporated liquefied gas, because this results in toxic environment around the vehicle due to CO and/or CO2 emission. For example, a garage would become a gas chamber.
Thus, liquefied gas needs the above mentioned special tank, wherein the gas must be highly pressurized, before fueling the tank, the so called compressed gas tank, of the automobile to provide a reasonable mileage.
Further, liquefied gas needs to be cooled in the liquefied gas tank. Therefore, either cooling is required or cost intensive gas management of evaporated liquefied gas is needed.
Consequently, there is a need to efficiently use the evaporated liquefied gas. There is also a need to store the liquefied gas, for example, in conventional tanks without special treatment. That is to say, there is a need to manage the evaporated liquefied gas, for example, in an automobile, in energy-saving and environment-friendly manner for widespread commercial use.
U.S. Pat. No. 6,798,083 B2 relates to a cryogenic power conditioning system for fuel cells, which is cooled by liquid hydrogen or liquid natural gas (methane) used to power these fuel cells, or by liquid nitrogen supplied by high-temperature superconducting cables.